1. The problem statement, all variables and given/known data This is a multi choice question from last years aqa a level. We know a positive reading is produced on the scales indicating something is pushing down on the scales. Please see the picture. 2. Relevant equations We know current direction, not B field. 3. The attempt at a solution The positive reading on the scales suggests that the force on the wire is vertically down. Mark scheme says vertically up. We think newton III is needed but not sure how it works. Can anyone help explain why i is vertically up.